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College of Science & Engineering > Department of Mechanical Engineering

Compressed Air Approach for Wind Energy Storage



(Warning: Under construction!)



Challenges of Wind Energy:

  1. Wind energy is intermittent and difficult to predict
  2. Timing mismatch between wind energy supply and power demand
  3. Integration of wind energy poses potential disruption of base power supply that cannot be turned on/off easily
  4. Wind turbines are under-utilized - typical capacity factor is less than 50%
  5. Installation, transmission, interconnection and other balance of plant costs are significantly higher for off-shore wind turbines than land based turbines

Benefits of energy storage localized to wind turbine:

  1. Provides predictable power output
  2. Increases energy capture 
  3. Electric generator, interconnect and transmission can be downsized for demand instead of supply
  4. Increase capacity factor
  5. By storing energy before generation of electricity reduces generation loss and keeps electrical components small

Benefits of compressed air energy storage (CAES):

  1. Highly scalable;
  2. Reasonably inexpensive
  3. Moderate ramp rates
  4. Good power and energy densities compared to alternatives
  5. Potential for high efficiency

Comparison with other energy storage approaches:

  1. Electric batteries:  high energy density (720kJ/liter); low power density, expensive; limited life; recycling issues
  2. Pumped hydro and reversed pumped hydro: site specific; low energy density (10J/liter per m-of elevation
  3. Conventional CAES: excess electricity is used to compress air (70bar) in underground caverns; used to boost efficiency of natural gas turbines; not a pure storage mechanism; overall efficiency is low;

Our Approach:  Isothermal Compressed Air Energy Storage (CAES):

  1. Store energy in high pressure (300 bar) compressed air vessel (~20m3 per MW-hr)
  2. Storage and regeneration via efficient isothermal air motor/compressor with enhanced heat transfer
  3. Open accumulator (patent pending) configuration for efficient and power dense operation
  4. Storage of energy prior to electricity generation
  5. Efficient hydraulic transmission for efficient, power dense and reliable operation
  6. Synchronous AC generator downsized for demand
Open accumulator configuration

Research Challenges:

  1. Effective heat transfer in air motor/compressor
  2. Efficient hydraulics and other machine elements
  3. Optimal system configuration, operation and control

System Overview:


Research Topics:

A multi-disciplinary approach is taken. Please visit each discipline below for details.

  Heat Transfer System and Control

Machine Design
Droplets and Nozzle Sprays

surface texturing

Surface Texturing

  Contact: Prof. Perry Y. Li
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